Thermostatic instrument.



c. s. JOHNSON. THERMOSTATIO INSTRUMENT.

APPLICATION FILED D130. 17, 1907.

Patented Feb. 16, 1909.

lmniinmm fii'tizeJJeJ. 6

embodying this invention.

CHARLES To all whom it may concern.

Be it known that 1, CHARLES S. JOHNSON, a citizen of the United States, residing in Boston, in the county of Suti'olli and State Massachusetts, have invented an Improvement in Thermostatic Instruments, of wlr' the following description, in connection with the accompanying drawings, '3 a specifics tion, like letters on the drawings rc 'ircsenting like parts.

This invention relates to a thermostatic instrument of that class having a movable strip or member which elongates under heat. Thermostats of the class referred to are usually provided with a fined member with which the movable member cooperates.

The present invention has for its object to provide a thermostat of the class described, in which the contact points oi the two members are protected from external influences, such as dust, moisture, etc, without interfering with the sensitiveness oi" the instrument.

Another feature of the invention consists in providing means for preventing the movable member from contracting abnormally for a purpose as will be described.

The invention further has for its object to provide for the circulation of air througl'i the instrument, so as to avoid dead air pockets and thereby render the instrument more sensitive.

These and other features of this invention will be pointed out in the claims at the end of this specification.

Figure 1 is an elevation of a thermostat Fig. 2, a p .11 view of the thermostat shown in Fig. 1. 3, a section on the line 3-3, Fi 2. Fi i, an underside view of the thermostat shown in Fig. 1, and Fig. 5, a section on the line 55, Fig. 2.

Referring to the drawings a represents base of porcelain or other insulating material, provided on its front side with chamber or pocket I), from which projects an annular flange 0. l i ithin the chamber 1) are located the movable member d and the stationary member a of the thermostat.

The movable member (X may be of any suit able or usual construction such as a coiled metal strip having one end fastened to a metal post f, and the stationary member e is shown as a screw extended through a metal post 9. The posts f, g, are extended through the base a and screwed or otherwise secured Specification of Letters Patent.

ion filed December 1'7, 198?.

earnnr JOHNSON, BOSTON, MASSACHUSETTS.

Patented Feb. 16, 1938.

Serial No. 405,837.

The end oithe movable member or thermostatic strip a cooperates with the stationary member or screw e, and in the present instance, said strip is normally out oi contact with the said screw, and the instrument is designed for use on open circr which is adapted to be clo hv a temperature to a given or point, as 3W a tire.

The present invention has for one of objects, to otect the contacting snrl'aces oi the movable and station '5 n nbers of the instrument, against d'rst, incisture, etc, without imp lring the sensitiveness and iiciency oi the inst! inent. 'rnrs is accomplished by enveloping r the coi'itacting suiiaces or points strnment with a (iece or body 10 of nonconducting material, which is fusible or plastic under heat, such ior instance as wax and which in the pr mt inst nee is ii'iterposed between the post g and a hack stop 12 which is shown as a projection on the wall of the chamber or pocket Z). The wax i0 preferably completely covers the contacting end of the screw 6 and 'lso the free end of the thermostatic stri thereby ital; protecting p s, such as dust, moisture, etc, and maintaining them for an indefinite tine in good working condition. The was: may be of such a character as will sci-ten at the telllpOi'ittiLlc it is desired the instrument should operate, so hat when the heat in the vicinity of the thermostat reaches a predetermined or given piont, the war; will soften suiliciently to 'mit unrestrained or free movement of the thermostatic strip, which is elongated by the heat and malies contact with the screw or stationar member of the instrument, thereby closing the euit and giving the alarm. It the heat in the vicinity of the thermostat should subside beiore the waX was melted, the latter would again solidify and remain effective as a protecting medium. The back stop 12 serves to prevent an abnormal movement of the thermostatic strip (Z away from the member e, which might take place when the instrument is exposed to a low temperature, as for instance, in the winter, which low temperature might otherwise contract the thermostatic strip to such extent as to draw the Wax away from the stationary member and thereby expose the contact surface of said member to external influences.

From an inspec tion of Fig. 4, it will be seen that the thermostatic strip cl can only have a predetermined or limited movement away from its cooperating member, which movement can be regulated by positioning the back stop with relation to the thermostatic strip and the post g. It will also be observed that the wax 1O interposed between the back stop 12 and the thermostatic strip d assists in preventing abnormal contractive movement of said strip. Provision is also made for preventing the formation of a dead air space in the chamber 5, which is accomplished by providing the back of the said chamber with one or more outlets or open ings, which are extended to the outside of the instrument. In the present instance, this result is obtained by providing the base with openings (see Figs. 2, 4 and 5), which are extended through the bottom wall of the chamber 6 and connect the same with the at- .iosphere at the'back of the base, a space being formed between the base and the ceiling, Wall or other structure represented by the line 16 (see Fig. 1) by lugs 17 on the back of the base. The formation of arcs between the conducting strips h, i, may be avoided by erecting on the back of the base a wall 19, which may be integral therewith.

' The base a may also be provided with additional lugs 20 arranged at the opposite ends of the conducting strips in line with the wall 19 to form abutmentsfor layers of wax, not shown, with which the conducting strips may be covered, if desired.

The members of the instrument may be protected from injury by a wire grating 21 inserted into the flange c and resting on a shoulder 22. It will be observed from in spection of Fig. 3, that the chamber 5 is practically open, thereby affording access of the heat directly to the-thermostatic members.

I have herein shown one construction of instrument embodying this invention, but I do not desire to limit the invention in this respect.

Claims.

1. In a thermostatic instrument, in combination, a base of insulating material provided on its front side with a chamber or pocket, posts within said chamber and extended through the back of said base, conducting strips secured to said posts on the back of said base, terminal screws engaging said conducting strips and extended through said base, a stationary member secured to one of said posts within said chamber, a movable member secured to the other of said posts and cooperating with said stationary member, and a fusible non-metallic material covering the contacting surfaces of said members, substantially as described.

2. in a thermostatic instrument, in combination, a base, cooperating members supported by said base and one of which is movable with relation to the other, a fusible nonmetallic material covering the contacting surfaces of said members, and a back stop cooperating with said movable member to limit its contractive movement away from its cooperative member, substantially as described.

3. In a thermostatic instrument, a base, cooperating members supported by said base and one of which is movable with relation to the other, a fusible non-metallic material covering the contacting surfaces of said -members, and a back-stop on said base sub stantially in line with the said cooperating members and cooperating with the movable member, for the purpose specifiedv 4. In a thermostatic instrument, a base provided with a chamber, cooperating members=supported by said base within said chamber and one of which is movable with relation to the other, a lug or projection integral with the base and located within the chamber in line with saic members to form a back stop for the movable member, substantially as described.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

CHARLES S. JOHNSON. Witnesses:

JAS. H. CHURCHILL, J. MURPHY. 

